This invention relates in general to the control of domestic appliances such as clothes washers, dishwashers, and the like, and in particular to an electromechanical control regulated by an electronic circuit including an integrated circuit programmable timer.
U.S. Pat. No. 2,703,347 to Constantine discloses a motor-driven control having a fixed array of switches sequentially actuated in predetermined patterns by a cam disc incrementally rotating at a fixed rate to effect the cycling of a domestic appliance, such as an automatic clothes washer or dishwasher, through a predetermined sequence of operations over a predetermined period of time.
The edge of the cam disc is toothed for engagement with a reciprocating pawl element driven by a constant speed motor. Thus, the cam disc is rotatably driven in ratchetlike fashion through a plurality of discrete angular positions at, for example, 6.degree. increments (60 discrete angular positions for each full revolution of the cam disc).
The dwell time of the cam disc (i.e., when the cam disc is at rest) at each of its angular positions is fixed and dependent upon the speed of the drive motor which interfaces with the ratchet action pawl element via a set of reduction gears, the dwell time being that period of time when the pawl element is reciprocating through a lost motion reset movement to engage with the next tooth on the edge of the cam disc. In effect, the constant speed motor, which is often of the synchronous type, acts as a timer to cycle the controlled appliance through desired operations over a period of time necessary, for example, to properly wash a dish or an article of clothing.
Because the dwell time as noted above is fixed, cycle operations requiring a period of time greater than the dwell time of the disc at a single angular position necessarily take up an arcuate sector of the disc in excess of 6.degree..
For example, the drying cycle of an automatic dishwasher takes a considerable amount of time relative to other cycle operations. Thus, with the drive motor operating continuously, a major arcuate sector of the cam disc is dedicated to the drying cycle, with the associated cam-actuated switch array remaining in a fixed pattern throughout such sector of cam rotation.
It is apparent that the prior art Constantine device discussed above, in combining both a timing function and a control function into a single electromechanical cam-type device, inherently limits the complexity and density of the program that can be fitted onto a cam disc of acceptable size.
U.S. Pat. No. 2,703,347 is herein incorporated in its entirety by reference.